The sarcophytol A was reported to exhibit anti-carcinogenic promotor activity [Cancer Surveys, 2, 540 (1983); Taisha, Vol. 25, Special Edition, Gan '88,3 (1988)] and anti-tumor activity [Japanese Patent Publication 20213/1988], whereby it has been regarded as a useful anti-tumor agent. As can be seen from the following structure, sarcophytol A is a cembrane type diterpene-alcohol containing one conjugated double bond and two other double bonds in the 14-membered ring. ##STR4##
The present inventors studied with the aim of developing a synthetic method of sarcophytol A and have proposed a synthetic route shown by the following synthetic route 1 [JP Patent Appln. 181710/1989; filing date: Jul. 14, 1989]. ##STR5## wherein R.sup.5 is C.sub.1 - C.sub.4 lower alkyl group or phenyl group; X is a halogen atom or a leaving group such as OSO.sub.2 R.sup.6 and the like; and R.sup.7 is a hydrogen atom , trimethylsilyl group or 1-ethoxyethyl group.
The process according to the above synthetic route 1 requires as the starting material a valuable compound having entire carbon atoms and structure essential for the production of sarcophytol A and comprises an oxidation of the terminal methyl group of said starting compound with selenium dioxide. However, since the oxidation at the terminal position is poor in the selectivity and yield, said process was not satisfactory for the industrial application.
Under these circumstances, the present inventors have investigated earnestly with the aim of developing an improved method for producing the intermediate [A] effectively and easily, thereby providing a process applicable to the industrial production of the final product, sarcophytol A, and have now found certain novel acyclic terpene compounds useful for the establishment of the purpose of the invention.